Predator and Prey Relationships

Coyote in Yellowstone National Park

A grazing elk

Predator: CoyotePrey: Elk

An elk calf

One of the most prominent predator/prey relationships is that of Coyotes and Elk. Predation on this larger mammal provides a vital food source for the coyote. Predation on Elk is seen on their calves shortly after birth as well as “short-yearlings,” which are elk just before one year old. Adult elk are pursued by the elk during the winter in Yellowstone. However, the coyote is not always successful. Researchers in Yellowstone have observed both successful and unsuccessful attempts at predation on elk calves. Occurrences of elk preying on adult elk are few and far between. Researchers Gese and Grothe observed nine winter attempts in Yellowstone in 1995. Only five of the nine attacks were successful. Evidence has suggested that the attacks on adult elk are more successful when they are led by the alpha male. Typically, coyotes attack larger prey from the rear or the flanks of the prey. Some studies show that coyotes attack in small groups, whereas others include all pack members. Elk serve as a very important organism in Yellowstone. The coyote population rests on the population of elk in the park. The coyote population increases when there are higher populations of elk, especially young elk.Coyote feeding on dead elk:http://www.youtube.com/watch?v=j_7kK2zpUHA

Growling gray wolf

Yellowstone elk

Predator: Grey WolfPrey: Elk

Gray wolf in the snow

The wolf population in Yellowstone National Park relies heavily on the elk population. Evidence shows that the wolf population decreases in direct proportion to the elk population. At the end of 2011, 98 wolves in ten packs lived within the limits of Yellowstone. However, in the Northern range of Yellowstone, the wolf population decreased approximately 60% since 2007 due to a decrease in the elk population. The elk serves as a main food source, especially for the Northern range wolves. A lesser effect was seen on the interior wolves, mainly because of the abundance of bison that the wolf also preys on. Yellowstone staff estimates 343 large game kills in 2011. 78% of these were elk. Approximately 27% of the elk killed were calves. The remaining percentages were 3% yearlings, 44% cows, 18% bulls, 3% adults, and 6% unknown age. The wolves have only decreased the elk population by 20% since their reintroduction into Yellowstone in 1995.

The Role of Predation

Wolf pups feeding

Grizzly bear fishing

Predation occurs when one predator feeds on its prey. Simply put, it is when one organism eats another. The act of predation results in the death of an organism and the eventual consumption of their tissue. Therefore, the predator may or may not kill their prey prior to consuming them. Predators tend to lower the survival of their prey, as well as their ability to reproduce. Predators also depend on their prey for survival. The effects of predators and prey on one another are signigicant. When a predator population is large, a decrease in the prey population is typical. Conversely, when the prey population is small, there is a decrease in the predator population. In Yellowstone, predation is a very important part of the ecosystem. It prevents overpopulation of a single species. For example, if elk did not have predators such as the gray wolf, then the population would expand rapidly, which would affect other organisms in the ecosystem. It holds population in balance and prevents one organism from dominating the area. There are many important predator and prey relationships in Yellowstone National Park that sustain the immense ecosystem.